Digit display apparatus

ABSTRACT

In a digit display apparatus of the type wherein a plurality of elongated digit elements are arranged in a basic digit pattern, the display portion of each digit element is made of a transparent material and each digit element contains a light cource, whereby any desired digit can be displayed by lighting the light sources of selected elements, transverse grid lines are formed on the rear surface of each digit element.

United States Patent [1 1 Nishina et a1.

[ DIGIT DISPLAY APPARATUS [75] lnventors: Rintaro Nishina, Yoneza va;

Tomokazu Suzuki, Tokyo, both of Japan [73] Assignee: Tamura Electric Works, Ltd.,

Tokyo, Japan [22] Filed: Feb. 25, 1974 [21] App]. No.: 445,104

[30] Foreign Application Priority Data Mar. [4, 1973 Japan v. 48-31674 Mar. 14, I973 Japan 48-31675 [52] US. Cl. 340/378 R; 340/383 [51] Int. Cl. G08b 5/36 [58] Field of Search..... 340/378 A, 382, 383, 378 R [56] References Cited UNITED STATES PATENTS 1,592,645 7/1926 Ramsdell 340/383 [451 July 15, 1975 2,115,906 5/1938 Dickson et 340/383 3.581307 5/l97l McKim et a1. 340/378 R 3,678,458 7/l972 Ljungkull et al..... 340/333 X 3,786,499 l/l974 Jankowski et al 340/378 R Primary Examiner-David L. Trafton Attorney, Agent, or FirmRo1and Plottel 6 Claims, 3 Drawing Figures 1 DIGIT DISPLAY APPARATUS BACKGROUND OF THE INVENTION This invention relates to digit display apparatus of the type wherein a plurality of digit elements. at least the display portions thereof being made of transparent material and each containing a light source such as an electric lamp. are arranged in a basic digit pattern such as a figure 8 form and the lamps of selected elements are lighted to display a desired digit.

From the standpoint of commercial value such display apparatus is required to be constructed such that the light emanated by the light source illuminates uniformly the display portion of each digit element for the purpose of eliminating any difference in the brightness at portions located at different distances from the light source and that the lighted lamp cannot be seen clearly. To this end, in the prior construction. the rear surface of the display portion of each digit element is frosted or formed with diamond prism cuts for randomly refleeting light but such construction are not always satisfactory.

SUMMARY OF THE INVENTION Accordingly. it is an object of this invention to provide an improved digit display apparatus ofthe type referrcd to above wherein the brightness of respective digit elements can be made uniform throughout the length thereof even when the light source cannot be located at the longitudinal center of the digit element.

Another object of this invention is to provide an im proved digit display apparatus of the type referred to above in which the light from the light source is caused to reflect randomly thereby making uniform the bright ness of each digit element over the entire length thereof.

According to this invention. there is provided digit display apparatus of the type wherein a plurality of elongated digit elements are arranged in a basic digit pattern such as a figure 8 configuration. the display portion of each digit element is made of a transparent material and each digit elements contains a light source whereby any desired digit can be displayed by lighting the light sources of selected digit elements, characterized in that transverse grid lines are formed on the rear surface of each digit elementv The grid lines are formed by serrations and the side surfaces thereof may be formed with fine irregularities.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. I is a front view, partly broken away ofa portion of one embodiment of the novel digit display apparatus embodying the invention.

FIG. 2 shows a sectional view of the display apparatus shown in FIG. I taken along a line lIlI;

FIG. 3 is an enlarged sectional view of a portion of a digit element taken along a line IIl-III in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The digit display apparatus illustrated in the accompanying drawings comprises a front plate 12 made of transparent material such as a sheet of glass. acrylic resin or the like. and the entire surface of the front plate I2 is covered by an opaque light shielding material 15 except a plurality of digit elements I4 (l-Ia through 14g) which are arranged in the form of a figure 8. The rear surfaces of vertical digit elements 1411. I41; I41 and I4fare provided with transverse or horizontal grooves 16 as shown in FIG. 3. In the same manner. horizontal digit elements 14a. 14d and 14g are formed with transverse or vertical grooves I7. On the back of each digit element I4 is provided a light guide 18 containing an electric lamp 19 at the bottom thereof. Such grooves can also be termed serrations or a plain grid.

In operation. the light emanated from each lamp I9 is guided by the light guide I8 to impinge upon the flat side surfaces of the grooves. The light reflected by the flat side surfaces of the grooves undergoes interference thus forming a type of spectrum which is transmitted through the front plate 12 to the outer side thereof.

In this manner. according to this invention. a portion of the light from the source propagates in the direction normal to the grid lines. that is in the longitudinal direction of the digit element. whereby the brightness ofthe digit element is averaged to eliminate the difference between portions close to and remote from the light source. For this reason. it is possible to obtain uniform brightness even when the light source not be located behind the longitudinal center of the digit element.

It is evident that the provision of a larger number of grid lines is advantageous. but as it is difficult to provide such a large number of grid lines by cutting it is preferable to use a replica of a diffraction grid as a digit element.

Further. when fine irregularities are formed on the side surfaces of the grooves as by etching process or sandblasting. random reflection of the light is resulted thus increasing the width of the spectrum. This makes more uniform the brightness and the lighted lamp invisible.

What is claimed is:

I. In a digit display apparatus of the type wherein a plurality of elongated digit elements are arranged in a basic digit form, the display portion of each digit element being made of a transparent material and each digit element containing a source of light whereby any desired digit can be displayed by lighting the light sources of selected digit elements. the improvement which comprises transverse grid lines formed on the rear surface of each digit element parallel to the short axis of each elongated digit element.

2. The digit display apparatus according to claim I wherein said grid lines are formed by serrations formed on the rear surface of the digit element.

3. The digit display apparatus according to claim 2 wherein the side surfaces of said serrations are provided with fine irregularities.

4. The digit display apparatus according to claim 3 wherein said fine irregularities are formed by chemical process.

5. The digit display apparatus according to claim 3 wherein said fine irregularities are formed by physical process.

6. The digit display apparatus according to claim I wherein each said source of light for any said digit element is disposed within a light chamber in the form of a truncated cone. the front face of said truncated cone comprising said digit element and being wider than the portion wherein the said light source is disposed. 

1. In a digit display apparatus of the type wherein a plurality of elongated digit elements are arranged in a basic digit form, the display portion of each digit element being made of a transparent material and each digit element containing a source of light whereby any desired digit can be displayed by lighting the light sources of selected digit elements, the improvement which comprises transverse grid lines formed on the rear surface of each digit element parallel to the short axis of each elongated digit element.
 2. The digit display apparatus according to claim 1 wherein said grid lines are formed by serrations formed on the rear surface of the digit element.
 3. The digit display apparatus according to claim 2 wherein the side surfaces of said serrations are provided with fine irregularities.
 4. The digit display apparatus according to claim 3 wherein said fine irregularities are formed by chemical process.
 5. The digit display apparatus according to claim 3 wherein said fine irregularities are formed by physical process.
 6. The digit display apparatus according to claim 1 wherein each said source of light for any said digit element is disposed within a light chamber in the form of a truncated cone, the front face of said truncated cone comprising said digit element and being wider than the portion wherein the said light source is disposed. 